1. Field of the Invention
The present invention is directed to a microprocessor-controlled dental instrument. More specifically, this instrument may be used in various dental treatments including removing areas of decay from a tooth structure, preparing a tooth for resurfacing, cleaning teeth, and the like.
2. Background of the Invention
The use of air abrasion in dentistry has been known for several years. Rosenberg, in the July, 1996 issue of Dentistry Today refers to air abrasion as the new standard in dental care. This article enumerates many advantages realized in air abrasion including increased patient comfort, alleviation of patient anxiety, decreased use of anesthesia, increase of dentists' productivity, and decreased costs to both patients and dentists.
Air abrasion instruments have been available for use by dentists for treating patients with an abrasive-laden fluid for many years. Such fluids include abrasive-laden air directed onto the patient's teeth for removal of decay, preparing the teeth to receive fillings, prophylactic treatment, and so on. Such abrasion instruments provide advantages over conventional dental drills. These include eliminating the heat, noise, and vibration produced by conventional high-speed drills. Also eliminated in many cases is the need for anesthesia as well as the need to cool the drill with fluid.
There are, however, issues of concern involved with the use of air abrasion. One of the desired improvements in this technology is to cut efficiently at moderate or low air pressures, while avoiding the use of potentially dangerous high pressure. Higher pressure (ranging from about 100-160 psi) increases the cutting speed of the air abrasion dental instrument, but this pressure level can be injurious for the patient causing such injury as air emphysema. Rosenberg, in the reference above, suggests using the lowest air pressure possible. Reasons cited include patient comfort and better control and visibility for the dentist.
Another disadvantage of using high pressures is that as the abrasive air fluid exhausts from the air abrasion instrument, an immediate drop in pressure occurs. This pressure drop causes the fluid to decrease in temperature. The static temperature of the fluid can decrease to, for instance, about 20 degrees Fahrenheit. At this temperature, air flow against a patient's tooth can cause extreme discomfort. In order to compensate for this, a heater may be needed. Another alternative to compensate for the coldness of the air stream would be to employ anesthetic, requiring the use of a hypodermic needle. Patient discomfort, the need for anesthetics, and the use of needles are contrary to the use of air abrasion dentistry. Since the lessening of patient anxiety and discomfort are basic tenets of air abrasion, these remedies for high pressure use are not acceptable.
In the past, various methods of feeding particulate abrasive have been attempted. Gallant in U.S. Pat. No. 4,708,534 discusses the use of particulate abrasive material in a pressurized gas stream. The stream is used to perform various procedures under uniform pressure.
The use of high pressure in abrasive jet machining is mentioned in U.S. Pat. No. 4,733,503 and U.S. Pat. No. 4,893,440 to Gallant et al. Disclosed herein is the use of high pressure using abrasive-laden gas streams. Pressures of several hundred psi up to 2,000 psi are disclosed.
U.S. Pat. No. 4,635,897 relates to a tube flow shut-off device. This shut-off device is for a tube formed of flexible material and adapted to carry a fluid. Control of fluid flow of the instant invention is microprocessor controlled. The entire operation of the unit of this invention is regulated by the microprocessor.
U.S. Pat. No. 5,618,177 to Abbott discloses an arrangement for feeding pressurized particulate material which overcomes several drawbacks of earlier air abrasion equipment. Microprocessor control is not one of the suggested improvements.
These prior examples of pressure use in air abrasion dentistry neither mention nor suggest the use of microprocessor-controlled pulsed mechanism for improved cutting efficiency and control of the instrument. Neither do they mention or suggest other methods of increasing particle speed besides the use of high pressure.
In an article in the March/April 1997 issue of Dental Practice & Finance, Bob Kehoe authored an article entitled "Assessing Air Abrasion". This article, which is intended to provide advice on the use of air abrasion dentistry, states that air abrasion is "designed to conservatively cut virgin teeth, remove sealants and composite restoration, not amalgam or other metals." In light of this recent assessment, the results of the applicant in removing amalgam with air abrasion techniques and the unit of the instant invention is a significant improvement.
Another publication doubting the possibility of amalgam removal with air abrasion appears in Reality NOW in the October, 1996 issue. In its ratings and updated commentary on air abrasion units, it lists amalgam removal as a contraindication for the use of air abrasive. Again, the results of the applicants in removing amalgam with air abrasion techniques and the unit of the instant invention is quite surprising and remarkable.
In another dental industry publication, DDRT (Dentists' Desktop Reference to Technology), Rosenberg mentions amalgam removal using air abrasion. He states that a supersonic nozzle employed in the instrument Mach 4.0 manufactured by Kreativ, Inc., the assignee of this invention, is key to successful amalgam removal using air abrasion. This article not does mention the unique features of the air abrasion unit of this invention, such as pulsing and microprocessor control thereof, and their importance to successful amalgam removal.